1. Field of the Invention
The present invention relates to an inhaler that is configured so as to be carried with the user and is used to effect efficient administration of a medicine for health care by ejecting and inhaling the medicine as minute liquid droplets.
2. Description of the Related Art
In recent years, average life span has lengthened due to progress in medical science and natural science, and an aging society is one result. On the other hand, people's anxiety about health has increased because of changes in eating habits and living environment, an increase in environmental pollution, and discovery of new diseases and infectious diseases caused by viruses and bacteria. Especially in the developed countries, the increase in patients with lifestyle-related diseases such as diabetes mellitus and hypertension has posed a problem.
On the other hand, the number of medical institutions has not increased in step with the increase in such patients, and some regions have no medical institution to which patients can go regularly.
Hereunder, description will be given by taking a specific example. Among patients with diabetes mellitus, the prevalence of which is increasing at present, patients with insulin-dependent diabetes mellitus (called “type I”) must take insulin periodically because insulin is not secreted by their pancreas. Since the insulin is administered by hypodermic injection at present, the user's physical and psychological burdens are heavy.
To reduce such user's burdens, a pen-type syringe that has a thin needle and scarcely gives pain has been developed. However, patients with type-I diabetes mellitus often lead the same life as that of healthy persons except for the need to self-administer insulin periodically. Therefore, even with a syringe of pen type, patients are psychological reluctant to given themselves an injection in the presence of other people, so that it is difficult to administer insulin at the proper time. As a result, such a method has a possibility that proper treatment of the user is not performed.
Also, chronic obstructive pulmonary disease (COPD) that seems to appear from chronic inflammation of the lungs due to smoking, etc., is also a lifestyle-related disease of the lungs that has received attention recently. In this disease, early symptoms are slight and difficult to notice, so that pulmonary function declines with age, which finally leads to chronic respiratory insufficiency and deterioration in the patient's general condition, hindering daily life. In many cases, the conventional treatment of COPD is performed by inhaling a medicine having bronchial tube expanding action by using a metered dose inhaler (“MDI”) or a dry powder inhaler (“DPI”).
A medicine ejection apparatus by means of which the user can take a medicine by inhalation, and which can make the most of an information database such as an electronic medical chart, is known for treatment of a patient. Such a medicine ejection apparatus has a storage unit for storing information about the individual user, including information of the user's medical chart and medical prescription. Such a medicine ejection apparatus, which is also a portable terminal that is also used as a medicine inhaler in which a medicine is ejected as minute droplets and is inhaled by the user, has a control section for controlling the inhaler to eject the medicine.
The medicine ejection apparatus as described above can exactly control the dosage of medicine according to the medical prescription. According to this, unlike the conventional medicine administration, a medical instrument such as a syringe need not be used at the time of medicine administration. Therefore, the operation can be performed easily without expert knowledge, and also the user is spared the pain caused by use of a needle.
Also, it is generally known that the intrapulmonary deposition of minute droplets of medicine caused by inhalation depends on the particle diameter of the medicine. For example, transmission to the vicinity of bronchial tube requires a particle-size distribution of about 7 μm of medicine diameter, and transmission to the pulmonary alveoli, which are deep in the lung, requires a narrow particle-size distribution of about 3 μm of medicine diameter. By applying inkjet technology, which has been fostered by development of printers performing highly fine printing, especially the thermal inkjet technology, to the ejection of medicine, a liquid medicine can be turned to minute liquid droplets having a narrow particle-size distribution. By this technology, more efficient medicine taking or more proper medicine transmission to a diseased part than conventional treatment can be realized (refer to International Publications WO95/01137 and WO02/04043).
Conventionally, at the time of medicine inhalation, the user's action for taking a breath, that is, the negative pressure produced in an air flow path by the inhalation, is detected by a pressure detecting unit, and the ejection is started in association with the output of the pressure detecting unit. At this time, if the medicine is ejected at the moment when the pressure detecting unit detects the negative pressure, the medicine is ejected if there is a temporary and minute pressure change produced by a change in usage environment rather than by the user's inhalation, and thus the medicine may be wasted. Such ejection is unfavorable in terms of hygiene as well. Therefore, generally, if the negative pressure in the air flow path exceeds a fixed value, it is determined that the pressure change is produced by the user's inhalation, and only then is the ejection of medicine started. That is to say, in order to start the ejection, the elapse of a predetermined time has been needed from the time when the inhalation has begun. Also, depending on the user's manner of inhalation, the time until the pressure reaches a pressure level at which it can be determined that the inhalation has been performed differs from person to person.
On the other hand, when medication is accomplished through the lungs, in order to absorb the medicine from the pulmonary alveoli into the human body most efficiently, it seems desirable that the medicine arrives at the farthest (deepest) part in the lungs. For this purpose, as is well known, it is ideal that the liquid droplets are borne on the air flow early during the time of inhalation. However, in the method in which the ejection is started after the predetermined negative pressure has been detected as described above, it is difficult to bear liquid droplets on the air flow early during the time of inhalation.